The skilled person in the food and beverage industry knows of the critical role flavor plays in the appreciation of food and beverages. Many food products, such as cocoa, chocolate, coffee, caramel, nuts, malt and the like have flavor quality that is referred to in the language of this art as "roasted brown." For purposes of the present invention, the term "roasted brown" will be used to describe flavor properties of the mentioned food products, as well as of food products having similar flavor characteristics. As used herein, the term "flavor" is intended to mean flavor, aroma and/or taste.
From the above group of food products, flavor is especially important for chocolate. Fine flavor, high nutritional value, pleasing appearance and good storage qualities make chocolate a food product of exceptional value which is very popular and widely used. The flavor of chocolate depends on the quality and origin of the cocoa beans, on the processing thereof and the preparation of the chocolate. The processing steps which influence the chocolate quality include fermentation, drying, roasting, cleaning and milling of the cocoa beans. In the preparation of chocolate, the ratio of cocoa mass, sugar and cocoa butter, etc. determines the flavor of the product. The flavor of chocolate has been thoroughly investigated and many volatiles contributing to the overall flavor have been determined (I. Flament, "Coffee, cacao and tea in Volatile compounds in foods and beverages," H. Maarse, Ed., Marcel Dekker, Inc. New York, 1991; Grosch, Lehrbuch der Lebensmittelchemie, 4. Ed. 1997). Compounds mainly contributing to the cocoa flavor are aldehydes, especially isovaleraldehyde and phenylethanal, as well as the corresponding aldol condensation product 5-methyl-2-phenyl-2-hexenal.
Many chocolate and cocoa based foods and beverages produced by the food industry lack flavor characteristics of high quality chocolate and cocoa. A great deal of effort has been expended to provide compounds with a natural chocolate or cocoa flavor for imparting the flavor of high quality chocolate and cocoa to products of low quality. U.S. Pat. No. 3,582,360 reportedly discloses unsaturated aldehydes, especially 2-phenyl-2-alkenals, for preparing flavor compositions and food products, particularly with chocolate and cocoa flavor.
Also, other food products with roasted brown flavor lack this freshly processed flavor. This short coming substantially reduces the overall organoleptic impression of the freshly roasted product. The missing flavor note is described as green, pungent and cocoa-like. The deficiency in roasted brown flavor is mainly due to a decrease of isovaleraldehyde. Isovaleraldehyde is relatively highly volatile, has a high reactivity towards alcohols, such as propylene glycol used as solvent in the flavorings, and undergoes aldol reactions with other aldehydes, such as phenylethanal, present in the flavorings.
The .alpha.-hydroxyketones are another example of a flavorant. .alpha.-Hydroxyketones are reportedly well represented in food products. One example is acetoin (3-hydroxy-2-butanone) which has a buttery, creamy character and which can be found in a great number of food products (Volatile compounds in food, qualitative and quantitative data, TNO Nutrition and Food Research, supplement 5, H. Maarse, C. A. Visscher, L. C. Willemsens, L. M. Nijssen, M. H. Boelens, Eds., 1994). The compound 3-hydroxy-5-methyl-2-hexanone was reportedly found in water buffalo milk and its odor (GC sniffing) was described as similar to melted cheese (L. Moio, E. Semon, J. L. Le Quere, Ital. J. Food Sci. (1994), 4, 441).
The literature reportedly describes different methods for producing .alpha.-hydroxyketones. For example, JP-A2-04120043 reportedly discloses the synthesis of .alpha.-hydroxyketones by oxidizing olefins with H.sub.2 O.sub.2 under acidic conditions. EP-A1-0 482 834 reports the preparation of .alpha.-hydroxyketones by oxidizing olefins with peracetic acids in the presence of an Ru catalyst. JP-A2-03167150 reportedly describes the synthesis of .alpha.-hydroxyketones by oxidation of alkynes with oxygen in the presence of silanes and a Co catalyst. JP-86-150522 reportedly describes hydrolysis of .alpha.-halo arylketones in the presence of alkalihydroxides to prepare .alpha.-hydroxarylketones.
From the discussion above, it is clear that there is a need for compounds which can be incorporated into, e.g., food and beverage products to impart roasted brown flavor thereto.
Accordingly, one object of the present invention is to provide compounds which are useful in imparting roasted brown flavor to food and beverage products.
Another object of the invention is a process for producing novel .alpha.-hydroxyketones.
These and other objects of the invention will become apparent from the disclosure and claims set forth herein.